Abstract The opioid partial agonist buprenorphine (BUP) is a highly effective but vastly under-utilized maintenance treatment for opioid use disorder (OUD). Under-utilization of BUP is especially pronounced in the adolescent and young adult populations. For example, only a few percent of adolescents with OUD receive buprenorphine, even though it is FDA-approved for treatment of patients ages 16 and older. Both the American Society for Addiction Medicine and the American Academy of Pediatrics recommend BUP treatment for adolescents but emphasize that a stronger evidence base for youth treatment is needed. The objectives of this project are to quantify and characterize age-related disparities in utilization of buprenorphine and other medication assisted treatments (MATs) and to acquire evidence about the effectiveness of MATs among adolescents and young adults with OUDs. Specifically, we will analyze treatment and outcomes data from a commercial insurance claims database with data from more than 50 million privately insured individuals. Using ?big data? will allow us to examine MAT patterns even among adolescents, despite low MAT prevalence. The large data set will allow us to acquire knowledge about real-world MAT effectiveness among youth that will complement the limited evidence available from randomized trials. In Aim 1, we will assess the prevalence of MAT among individuals diagnosed with OUD by age, type of treatment, length of treatment (i.e., maintenance vs. detoxification only) and over time. We will examine the demographic and geographic correlates of MAT utilization, with particular emphasis on how prevalence has changed over time and how they might vary by age. We will examine use of different types of medication and medication change patterns (e.g., switching from buprenorphine to naltrexone). This will be an important first step in documenting and characterizing age-related disparities in MAT. In Aim 2, we will compare outcomes of MAT and non-MAT treated youth with OUD. We will use survival analysis to compare time to claims for relapse events. We will examine whether associations between MAT treatment trajectory and relapse outcomes vary by age, contrasting adolescents, young adults, and adults over 25. We will use both conventional propensity score matching and more advanced quasi-experimental methods. The latter analyses will leverage quasi-random variation in MAT prevalence by place and time to compare outcomes among groups of treated individuals with appropriately matched groups from environments where treatment is rare. Execution of this two-year project will be a critical first step toward a marked expansion of the evidence-base for MAT among adolescents and young adults that will provide critical information about promising treatments for a grave public health problem.